Potassium Cyanide
by naiYin
Summary: Everyone knows that you don't play around with Rokudo Mukuro. In fact, certain death was a risk you ran regardless of who you were. Even if your name was Sawada Tsunayoshi. Even if he promised. 'Cyanide is amongst the fastest acting poisons known to man.'


Potassium Cyanide

Rating: Teen

Warnings: It's a surprise~

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><p>Q: <em>How fast can potassium cyanide kill you?<em>

A: _Cyanide is not exceptional with regards to the amount needed to kill you, 200mg (0.2grams) is the accepted oral lethal dose for an average sized man. There are hundreds of other poisons which are more toxic, Arsenic Oxide and Strychnine being just two common examples. However, what makes cyanide so notorious is the speed that it acts. Cyanide is amongst the fastest acting poisons known to man._

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><p>The real Mukuro was bright, steady fire, attracting all the unwary towards its uncharacteristic warmth. It would do well to remember that just the inhalation of too much smoke would be risky. Being licked by the flames would be even worse—the scars it left behind would never fade. What couldn't be seen, not even by the most cautious individual, would be the source of it all. One clear core, filled with liquid cyanide. The barest taste of the poison hidden within and it'd mercilessly burn you from inside out.<p>

**—smoke can appear without warning—**

The first time Tsuna was kissed by Mukuro, under an awning one rainy afternoon, he knew something was wrong. Mukuro's gentle caress, softened eyes were hypnotic, but his intuition told him otherwise. That time, he had managed to shove Mukuro away, escaping the scene utterly confused with his conflicted feelings inside.

Mukuro wasn't a man of fluffy love and sprinkles. He was a possessive bastard with nothing in mind but his own gain. He learned this the hard way during the Kokuyo disaster, and though Mukuro seemed to have mellowed afterwards, Tsuna knew Mukuro was still extremely dangerous. Tsuna knew this, and yet Mukuro's poison was so subtle he couldn't bring himself to care.

When he found Yamamoto kissing a blushing Gokudera into the wall one day at Vongola Base, Gokudera backed up and hit the baseball nut hard on the head, apologizing furiously at the atrocity he had committed and that his precious Juudaime had witnessed it. Yamamoto laughed it off as usual, telling Tsuna not to worry, but Tsuna knew that the threatening glint his saw in Yamamoto's eyes when he first walked into them was not one from surprise or embarrassment.

That look was definitely one of angry reproach.

Tsuna's heart broke as he realized he had interfered with them. His best friends had each other, and while Gokudera was too tsundere to admit it, the message was clear: he wasn't wanted there. Even Tsuna, socially inept as he was, understood that much. Tsuna fled as quickly as he could, finally stopping in his office where he curled into a ball on the sofa and cried. He didn't complain when Mukuro materialized beside him, gently stroking his hair, slowly showering him with affection. He made Tsuna feel needed in way Gokudera or Yamamoto never could, he just laid back, took everything Mukuro gave and forgot everything that troubled him, letting the soft spoken words of love just wash him away.

**—and when there's smoke, there's fire—**

For awhile, Tsuna was happy, enveloped in Mukuro's overwhelming presence. Gokudera vehemently disapproved of Tsuna's relationship with the Mist Guardian, protectively hovering over him for hours on end. Tsuna ended up ordering his Storm Guardian to return to his own quarters, feeling far too smothered. It wasn't as if he didn't appreciate the effort Gokudera spent on him, but he was guilty for always stealing away time that the other should have been spending with Yamamoto.

Tsuna soon became so blinded by the unadulterated affection that he fell under the misconception that he would be safe with Mukuro, the same man who had aimed to kill him and all his friend, still pining to posses his body and the underworld. A fact he had obviously chosen to overlook. He thought, for just a small moment, just one bit of selfish thought, that he was special. He, Dame-Tsuna, 10th boss of the Vongola, would be the one to break through Mukuro's defenses before anything got to him.

As he slowly relinquished his doubts, it eventually brought them to a point where the Mist actively visited Tsuna in his house every night. Gokudera held his tongue to the best of his ability, although Mukuro because the foremost victim of his daily glare quota. Their rendezvous spot was always in the kitchen and they'd always part from there in the morning. The brunet had yet to offer him breakfast, in an attempt to have him stay. Their connection wasn't deep enough for that yet.

"Hey, Mukuro?"

"Yes, my little Tsuna-chan?" Mukuro had replied while leaning blithely on the kitchen table. His gaze was set on Tsuna, looking him up and down with an expression normally described as nothing less than predatory, one that Tsuna wrote off as not something to be worried about, once again ignoring his twitching intuition, when in fact he should have been extremely worried. Disturbingly, even.

"You might want to leave. Reborn will be up soon."

Mukuro stopped momentarily in his observation and focused his attention on Tsuna's eyes. "I'm sure he already knows of our relationship."

Tsuna shifted uncomfortably under his discerning eyes. "I know. I just don't want him to see you here."

"I wouldn't mind," Mukuro paused, smirking. "It's because you wouldn't like it, isn't it? You don't want the publicity on us. The whole of the underworld would know that you have me, and no one else." He stepped forward and loosely wrapped his arms around Tsuna's thin waist, breath hot in the brunet's ear. "You don't want them to know because you'd be jealous~."

Tsuna blushed slightly at the gentle rebuke. Yes, it was partly concern for Mukuro, but mostly jealously and an attempt to monopolize him.

Tsuna didn't realize how far Mukuro had already penetrated his own barricades. It didn't occur to him that he wasn't helping Mukuro recognize his mistakes, that it was nothing nearly as righteous. He was simply lonely.

"You're so cute when you don't know what you really want. Make me stay, Tsuna. Order me to stay with you." The command surprised him, and he tensed slightly in the hold that surrounded him, suspicious of Mukuro's motives, if only for a second. Then the soft, rhythmic breath and slight tightening in the arms around his waist convinced Tsuna that he was worrying without a cause. The illusionist had proven that he could be trusted, right?

Sighing, he grasped the taller man's arms, the movement an indication of how much he didn't want Mukuro to leave. "Stay with me." He turned around to stare into the other's mismatched eyes, searching for a key to understanding what the Mist was feeling at the moment. Then he abandoned the futile attempt to comprehend the other's thoughts, burying himself in the chest before him, taking in the scent desperately, like it would be the last thing he'd ever smell. "Forever, Mukuro." He whispered the word like it was sacred and taboo, all at the same time, scared for how the other would respond. Tsuna knew quite well that as far as Mukuro's attentions went, it would be foolish to expect anything. He was far from the best option around.

Unbeknownst to Tsuna, the man that held him was wearing a twisted grin. Though it was a bit dull to have prey that was predictable, versus, say, Hibari Kyouya, it was a nice change to know that everything was going completely as planned. "Only for you, little darling." Oh yes, Sawada Tsunayoshi would soon be entirely his.

—**fires can burn until there's nothing left—**

The morning had been normal. Mukuro was lying sideways on the table, poking at the pineapple centerpiece with an expression of bitter concentration. Tsuna had laughed at his boyfriend's antics, giving the fruit a kiss before greeting the actual man in question. Mukuro wasn't the only one who knew how to tease, after all.

Mukuro gave a hurt pout and Tsuna sighed, letting the other tug him in a for a good morning kiss. He liked it when the illusionist was affectionate, and although his sixth sense kept pulling at the edges of his mind to keep his defenses up Tsuna couldn't bring himself to distrust to taller man.

"Are you excited for the mission today?" It was a completely off-topic question. Mukuro never discussed anything 'work-related' when he was with Tsuna.

He frowned at the reminder, wondering what Mukuro was up to. "Not particularly… That family has proven itself untrustworthy many times already." Unlike you. "So we'd be best to be on guard."

Mukuro hummed. "As I thought, it's boring to talk about Mafia business with you. Let's not worry about that shall we? Where's breakfast?"

Tsuna smiled, deciding to follow the other's suggestion and forget about the nasty business later in that day for the moment. "You're always so impatient for food, Mukuro." It was a playful reprimand.

"Only because it's your cooking, my little darling."

He tried to stop himself from blushing, failing at it like he did most things. He muttered softly, smile showing he appreciated the thought. "It's not even good."

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><p>Turns out they were a lot less trustworthy than Tsuna had expected. Their Don had taken great pains to take them on a tour throughout their whole base, quite excitedly showing them all the things that proved their loyalty to the Vongola.<p>

Mukuro had been the first to spot something wrong. "Tsuna, have you noticed how often the guards are passing by?"

Reborn tilted his head up towards the illusionist approvingly. He had taken out Leon in gun form and had it armed and ready to the side. Tsuna retraced his memories back to when they had arrived. "I haven't seen any at all. That's weird."

"You'd almost think they were hiding for an ambush, wouldn't you?" Mukuro smirked. Far too predictable. The Family boss led them into the round library in the deep center of their base.

"I'm sorry, Tsunayoshi Sawada, but we had no choic-" Mukuro had stabbed his trident clean through the burly man's chest.

"Tsuna, run!" Reborn was already turning towards the shutting exits. Masked, armed men began dropping from the ceiling. For a routine visit, things certainly had taken a rapid change for the worse. The brunet was frozen as he quickly came up with several ways to resolve the situation without any bloodshed.

He gave Mukuro a horror struck expression as the dying Don behind him pulled out a gun, whispering only one word. "Traitor…" Tsuna didn't have the time to comprehend why the attacking Family's head would call one of his own people a traitor. He was already lunging forward to knock Mukuro out of the bullet's way.

It struck him like the feeling of Lambo's box weapon, Udon, broad siding him with its horns. He let out a startled gasp, then sank to the ground relieved. Reborn began picking off all the attackers that were closing in on the two injured Mafia heads.

Mukuro cradled the younger boy's head, eyes concerned and checking the wound. It was deep, and meant to be fatal. "You love me, don't you?"

"Yeah." Tsuna coughed and spluttered slightly. It was like a bad action movie.

"You'd do anything for me."

"Of course, Mukuro..."

"That's that, then. You've stopped amusing me." He gave Tsuna the most beautiful and perfect smile the boy had ever seen on him. "We're done, Sawada Tsunayoshi." Mukuro pulled away with Tsuna's blood still on his hands, standing up and walking away. Reborn had rushed up to check on the Don's status, the emergency medical team already well on its way. But it would doubtlessly be too late. His 'boyfriend' had made certain that the bullet path would be lethal if Tsuna hadn't received medical attention within thirty seconds. The same thirty seconds in which he'd finally pulled out the confession he wanted.

It was perfect. "Sleep well, little darling. I'll see you in hell."

**—but only poison will always kill—**

_Mukuro was potassium cyanide. Mukuro was death._

_You cannot trust death. You cannot fix death. The only thing you have to trust you own intuition, because in the end, you just aren't special._

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><p>AN: Just to make things clear, during the nights Mukuro has in Tsuna's room, they're either talking or sleeping. Not having sex, you sick children. 8D In fact, by the time Tsuna dies in this fic, he's still a virgin. Sad, isn't it?


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